Kiribati is traditionally regarded as the first country to enter a new calendar year because of its time zone.
Kiribati is an island nation spread across the central Pacific Ocean. Its Line Islands, including Kiritimati, use UTC+14, the world's most advanced civil time zone. As a result, midnight arrives there before it reaches most other inhabited places.
The country moved the International Date Line around its eastern islands in 1994. The change placed all of Kiribati on the same calendar day, ending the unusual situation in which parts of the country were separated by an entire date.
“First country” is a convenient shorthand, not a claim that every part of Kiribati reaches midnight simultaneously with every other part. The nation spans several time zones. Kiritimati is the location most often mentioned in New Year's coverage, while nearby Samoa and Tonga also experience the new year very early.